Electric clocks with magnetic drives

ABSTRACT

An electric clock employs a mechanical oscillator which is driven at its natural frequency and which contains a magnetic drive for driving the clock. The magnetic drive contains a nonmagnetized ferromagnetic pole spider, which on its circumference has disposed a single ring of magnetic poles. The poles of the magnetic drive which interact with the spider poles are assymmetrically positioned with respect to poles on opposite sides of the circumference of the pole spider.

United States Patent Inventor August Mutter Schwenningen (Neckar),Germany Appl. No. 738,977 Filed June 21, 1968 Patented May 11, 1971Assignee Muller-Schlenker Schwenningen (Neckar), Germany Priority June27, 1967 Germany ELECTRIC CLOCKS WITH MAGNETIC DRIVES 13 Claims, 10Drawing Figs.

US. Cl 58/23, 310/36 Int. Cl G04c 3/00 Field of Search 58/23, 23 (D), 116,23 (V), 116 (M); 310/36, 46, 152, 156; 74/25, 1.5, 126

[56] References Cited UNITED STATES PATENTS 3,208,287 9/ I965 lshikawaet al.

Primary Examiner-Richard B. Wilkinson Assistant ExaminerEdith C. SimmonsAttorney-Craig, Antonelli, Stewart & Hill ABSTRACT: An electric clockemploys a mechanical oscilla= tor which is driven at its naturalfrequency and which contains a magnetic drive for driving the clock. Themagnetic drive contains a nonmagnetized ferromagnetic pole spider, whichon its circumference has disposed a single ring of magnetic poles. Thepoles of the magnetic drive which interact with the spider poles areassymmetrically positioned with respect to poles on opposite sides ofthe circumference of the pole spider.

Patented May 11, 1971 3,577,874

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406437 Mun-{R aw/W ELECTRIC CLOCKS WITH MAGNETIC DRIVES The presentinvention relates to an electric clock with a time-determiningmechanical oscillator excited at its natural frequency and carrying amagnet system which drives the clock and the poles of which are disposedopposite two substantially diagonally opposed points of a nonmagnetizedferromagnetic pole spider, said mechanical oscillator moving said polesin substantially radial relation to said pole spider, to which a rotarymotion in synchronism with the movements of said oscillator is impartedby the movements of said magnet system.

An example of a clock of this kind is shown in US. Pat. No. 3,212,252.ln these known clock-s, the pole spider consists of a disc punched outof a sheet of iron and provided with circumferentially disposed radiallyprojecting teeth and, additionally, a ring of radial webs disposed in astaggered arrangement with respect to said teeth and separated byrecesses between the individual webs. The known pole spiders are thusprovided with two concentric rings of staggered poles. The manufactureof such discs is comparatively difficult since the punching tools callfor a plurality of pins and corresponding openings in the die plate,which are rather'diffrcult to make, especially in view of the requiredtrapezoidal shape. Furthermore, the pins of such tools tend to break, astheir cross sections are very slim.

Another clock provided with two rings of staggered poles formed byraised portions of a disc made of a magnetic material of highpermeability is known. A disc of this kind is also very difficult tomake.

In yet another clock, the pole of a magnet is disposed opposite thesinusoidal rim of a ferromagnetic disc and moved by a plate-typeoscillator in a direction perpendicular to the plane of the disc. Owingto the absence of salient poles the synchronizing forces are very weakso that the disc tends to fall out of step and additional means arerequired for stabilization. In the known clock, stabilization isachieved by'means of a flywheel 52. It is, however, a particulardisadvantage that the magnet exerts a continually changing radial pullon the disc which tends to set up lateral vibrations in the shaftsupporting said disc and subjects the shaft bearings to substantialunidirectional radial loads so that a special design is required forsaid bearings. Nevertheless, this alternating unidirectional friction inthe bearings adversely affects the rate of the known clock and leads torapid wear.

Furthermore, a clock in which a bar magnet oscillates in a directionperpendicular to the rim of a disc which is itself magnetized in such amanner that unlike poles alternate along its circumference is known. Themanufacture of such polarized discs is expensive and necessitates theuse of discs of a considerable thickness in order to achievemagnetization transversely to the disc. Again, the oscillating magnetexerts unidirectional radial forces on the disc entailing the samedisadvantages with respect to the bearings as detailed above.

Pole spiders of the kind first above described, i.e., spiders with tworings of staggered poles, have been employed not only in the movementsof clocks, in which a driving torque is applied to the pole spider bythe oscillating magnets, but also for magnetic escapements, in which thepole spiders are driven while the oscillators are not self-excited. Sucharrangements are known, and furthermore the use of a disc with asinusoidal rim for a magnetic escapement is known. It is noted that awave-shaped rim of this kind also forms two rings .of staggered polesdisposed at the peaks of the sinusoidal rim so that this arrangement,too, features two concentric rings of staggered poles. Magneticescapements with only one ring of poles are disclosed in U.S. Pat. No.3,132,522. In these arrangements, the poles of a horseshoe magnetsimultaneously approach, or move away from, one or two diagonallyopposed poles of the disc, so that the alternating effect of the knowndrives, which consists in that the magnetic pole as it moves away fromone pole of the disc approaches the disc pole staggered with respect tosaid first pole of the disc and thus produces a driving torque, ismissing in this case. These known arrangements are, therefore, unfit forapplying a driving torque .to the pole spider and can thus be used formagnetic escapements only, but not in clocks with a magnetic drive ofthe kind first above described.

It is thus apparent that the known electric clocks with magnetic drivewhich use a pole spider with two concentric rings of staggered poles arethe least complicated and that they offer an additional advantage inthat the spider and the bearings are not subjected to any axial orradial forces. It is the object of the present invention to furthersimplify these known arrangements.

According to the invention, this is accomplished by providing the polespider with only one ring of poles along its circumference, in a mannerknown per se from magnetic escapements, and by disposing the poles ofthe magnet system so that they will be located between two poles at oneside of the spider when they are opposite a pole on the other side ofthe spider.

The invention thus enables pole spiders to be used which have only onering of poles and are, therefore, very much easier to manufacture thanthe pole spiders previously used in electric clocks. The necessarydriving torque is nevertheless achieved, since the'arrangement of themagnet system according to the invention is such that as the distancebetween the magnet system and the .one pole is increased the distancefrom the following pole is again decreased so that the next pole isattracted. The present invention thus provides a substantialsimplification without affecting the timing accuracy of the clock.

The desired arrangement of the poles of the magnet system with respectto the poles of the spider may be achieved, for example, byappropriately staggering the poles of the magnet system with respect toeach other or by slightly displacing the magnet system with respect tothe plane extending through the arbor of the pole spider. However, in apreferred embodiment of the invention the poles of the magnet system aredisposed, in a manner known per se, in a plane extending through thearbor of the pole spider and the pole spider is provided with an oddnumber of poles.

A further embodiment of the invention provides for a pole spider withradially projecting teeth the ends of which are .bent off in thedirection in which the pole spider rotates. Preference is given to anembodiment in which the ends of the teeth of the pole spider areprovided with lugs projecting at a right angle in the direction ofrotation. This ensures a particularly smooth transition from one pole toanother so that the spider runs very quietly, thus obviating the needfor the lowfriction flywheel arrangements on the pole spider shafts ofthe known clocks. By properly dimensioning the bent off ends of thepoles it is even possible to provide for a self-starting feature, whichconstitutes an additional advantage of the present invention.

The oscillator and the magnet arrangements may take a great number ofdifferent forms. For example, a horseshoe magnet extending in a planeparallel to the pole spider and having its poles disposed oppositediagonally opposed points of the pole spider may be attached to theoscillator. Alternatively, the oscillator may be provided with twohorseshoe magnets, each extending in a plane perpendicular to the polespider with the poles of each magnet enveloping the pole spider from twosides at one of two diagonally opposed points of the spider. Thelast-mentioned arrangement affords the particular advantage that apartfrom the driving torque no forces are applied to the pole spider by themagnet system. The magnets may be attached to the ends of a vibratingreed, which may be formed by one leg of a tuning fork while the otherleg of the fork carries a suitable balance weight. Alternatively,magnets may be attached to both legs of a tuning fork.

The pole spider itself may, for example, consist of a toothed disc offerromagnetic material, especially sheet iron. Such a disc may bemanufactured in a very simple manner by punching it out of a sheet ofmetal without any pins being required to provide openings, except one tomake the central hole for the hub. Alternatively, the pole spider may bemade from a nonmagnetic material and provided with ferromagnetic insertssuch as radially or axially disposed pins.

Further details and embodiments of the invention will become apparentfrom the following specification, in which the invention will bedescribed and explained more fully with reference to the embodimentsshown by way of example in the accompanying drawing. In otherembodiments of the invention, the features apparent from thespecification and the drawing may be applied'individually or in anydesired combination.

Reference will now be made to the schematic representations of theaccompanying drawing, in which:

1 FIG. 1 is a top view of a first embodiment of the invention with aflat magnet yoke the ends of which are disposed opposite diagonallyopposed points of the pole spider,

FIG. 2 is a side elevation of an embodiment according to FIG. 1 in thedirection indicated by the arrow II,

FIG. 3 is a top view of a further embodiment of the invention with twohorseshoe magnets at the ends of a U-shaped support,

FIG. 4 is a side elevation of the arrangement according to FIG. 3 in thedirection indicated by the arrow IV,

FIG. 5 shows the arrangement of a magnet system on a vibrating reed,

FIG. 6 shows the arrangement of a magnet at the end of one leg of atuning fork,

FIG. 7 is a top view of a further embodiment of the invention withhorseshoe magnets at the ends of both legs of a tuning fork,

FIG. 8 is a side elevation of the embodiment according to FIG. 7 in thedirection indicated by the arrow VIII,

FIG. 9 is a top view of a further embodiment of the invention with apole spider provided with teeth bent off at a right angle, and

FIG. 10 shows an embodiment similar to that of FIG. 9 with teeth bentoff at an oblique angle.

In the embodiment shown by way of example in FIGS. 1 and 2, the ends ofa mechanical oscillator I, which is free to oscillate in the directionindicated by the double arrow 2, are provided with a magnet arrangementconsisting of a short bar magnet 3 and an essentially U-shaped magnetyoke 4, the ends 5 and 6 of which are bent off towards the inside sothat they are disposed in spaced relation to each other on a straightline 7 parallel to the direction 2 in which the oscillations occur.Between the ends 5 and 6 of the magnet yoke 4 there is disposed a polespider 8 provided with an even number of radially projecting teeth 9which constitute the poles of the spider. The pole spider 8, like themagnet yoke 4, may be punched out of a sheet of ferromagnetic materialof high permeability. The arrangement is such that the yoke 4 and thepole spider 8 are disposed in closely spaced parallel planes and that'the outside diameter 10 of the pole spider is slightly greater than thedistance between theends 5 and 6 of the yoke. Furthermore, the arbor 11of the pole spider is displaced with respect to the centerline 7 of theyoke ends 5 and 6 by an amount sufficient to ensure that the one end,for example end 6, will be located between two teeth 9 of the polespider when the other end 5 is opposite a pole 9, and vice versa.

If the pole spider 8 rotates counterclockwise, i.e., in the directionindicated by the arrow 12, and if at the moment represented in thedrawing the oscillator I is deflected from its central position towardsthe left, that tooth of the pole spider which is then within reach ofthe left-hand end 5 of the magnet yoke' is released while the toothapproaching the right-hand end 6 of the yoke is attracted andaccelerated by that end. If the oscillator is then deflected from itscentral position towards the right, the tooth which has just beenattracted by the right-hand end of the pole shoe is released again,while the following tooth is drawn into the range of the left-hand endof the magnet yoke. The pole spider 8 is thus rotated in synchronismwith the oscillations of the oscillator 1 and, may be used to drive atime indicator, connected to the shaft 13 of the pole spider.

In this embodiment of the invention, which is of a particularly simpledesign, the pole spider is loaded in the axial direction. Such axialloading may be prevented by the use of two magnet yokes 4 disposed oneither side of the magnet 3 and, simultaneously, on either side of thepole spider 8.

The embodiment of the invention according to FIGS. 3 and 4 differs fromthe embodiment according to FIGS. 1 and 2 in that a U-shaped yoke 22provided with a horseshoe magnet at each of its ends 23 and 24 isattached to the free end of the oscillator 21. These horseshoe magnetsare located in a plane perpendicular to the pole spider 25 and aredisposed so that the teeth 26 of the pole spider pass between the poles27 and 28 of the magnets. Furthermore, the poles of the magnets are, inthis case, disposed in a plane 29, which intersects the arbor 30 of thepole spider. To ensure that nevertheless the poles of the one magnet, inthe drawing identified as magnet 24, will be located betweentwo teeth ofthe pole spider when the poles of the other magnet are opposite theteeth of the pole spider, the pole spider is provided with an odd numberof teeth.

The operating principle of this drive is the same as that of theembodiment according to-FIGS. I and 2, except that the lines of magneticforce run through the teeth of the pole spider between the poles of eachof the two magnets only rather than extending diagonally across the polespider. Thus, it would also be possible to use a pole spider ofnonmagnetic material in which suitable poles of magnetic materialareinserted instead of a pole spider made of magnetic material. Withthis magnet arrangement no radial or axial forces of any kind act on thepole spider. The magnets 23 and 24 may be attached to the U-shaped yoke22 or may be formed directly by the magnetized ends of said yoke.

As shown schematically in FIG. 5, the oscillator 32, which supports theU-shaped magnet arrangement 31, may be formed by a baror plate-typeoscillator, e.g., a leaf spring, which is restrained at its other end.Alternatively, the U- shaped magnetarrangement 31 may be attached to oneleg 33 of a tuning fork, the other leg 34 of which is provided with abalance weight 35, as shown in FIG. 6. In either case, the oscillator isexcited, in a manner known per se and not shown in detail, with the aidof electromagnetic arrangements which are part of electronic oscillationgenerators.

Similar to the embodiment of the invention shown by way of example inFIGS. 3 and 4, the embodiment according to FIGS. 7 and 8 again uses twohorseshoe magnets 41 and 42, which are disposed in planes perpendicularto the pole spider 43 and the poles 44 and 45 of which envelope the polespider from two sides. However, unlike the magnets of the embodimentaccording to FIGS. 3 and 4 the magnets 41 and 42 are disposed at theends of the legs 46 and 47 of a tuning fork. This arrangement offers theadvantage that the rotation of the pole spider '43 is effected by bothlegs of the tuning fork so that the tuning fork is damped to a lesserdegree, which results in a higher efficiency.

Again the pole spider 43 has an odd number of teeth and the poles 44 and45 of the magnets 41 and 42 move in a plane which intersects the arborof the pole spider. In this case, the pole spider takes the form of anonmagnetic disc, in which radial pins 48 serving as poles are inserted.Furthermore, the pole spider 43 is laterally displaced with respect tothe centerline 49 of the tuning fork by an amount sufficient to ensurethat the poles of the magnet 41 will be located at the outer ends andthe poles of the magnet 42 at the inner ends of the pins 48 when thetuning fork is not oscillating. This arrangement is necessary to ensurethat when the magnets oscillate towards each other the magnet poles willalternately move in and out between the poles of pole spider 43. The useof a nonmagnetic disc with inserted poles is, in this case, particularlyadvantageous inasmuch as the right-hand magnet 42 will then not encloseany magnetic material between its poles during its inward deflection,which otherwise might produce a damping effect on the motion of the polespider 43. In all other respects, this arrangement operates on the sameprinciples as described with reference to FIGS. 1 and 2.

The arrangements according to FIGS. 9 and 10 are substantially the sameas those of the embodiment according to FIGS. 3 and 4, except that thepole spiders are provided with teeth of a different shape. In theembodiment shown by way of example in F IG. 9, the ends of the teeth 51of the pole spider 52 are provided with lugs 53 projecting from theteeth 51 at a right angle and extending in the direction 54 in which thepole spider rotates. This arrangement ensures that when the pole spider52 rotates in synchronism with the oscillations of the magnet system 55the front edge 56 of the lug 53 will always be opposite the pole shoes57 of the magnet system as these pole 'shoes move into the range of thepoles so that a driving torque is applied to the teeth 51 of the polespider 52 while the rotary motion of the pole spider is stabilized. Thisobviates the need for additional measures to prevent the rotor fromfalling out of step or stalling as a result of shocks and torsionalvibration.

As an alternative to the embodiment according to FIG. 9,

FIG. shows an embodiment in which the teeth 61 of the.

pole disc 62, at their ends 63, are bent off at an oblique angle in thedirection of rotation 64. This design, too, ensures a stabilization ofthe rotary motion.

it shall be understood that the present invention is not restricted tothe embodiments shown by way of example, but that deviations therefromare possible without leaving the scope of the invention. This appliesboth to the design of the pole spider and the design of the magnetsystem and the mechanical oscillator moving the magnet system.

lclaim:

1. An electric clock with a time-determining mechanical oscillatorexcited at its natural frequency and carrying a magnet system whichdrives the clock and the poles of which are disposed opposite twosubstantially diagonally opposed points of a nonmagnetized ferromagneticpole spider, said mechanical oscillator moving said poles insubstantially radial relation to said pole spider, to which a rotarymotion in synchronism with the movements of said oscillator is impartedby the movements of said magnet system, characterized in that said polespider is provided with only one ring of poles along its circumference,and in that the poles of the magnet system are disposed so that theywill be located between two poles at one side of the pole spider whenthey are opposite one pole at the other side of that spider.

2. A clock according to claim 1, characterized in that said pole spideris provided with an even number of teeth, and in that said poles of saidmagnet system are displaced with respect to the plane extending throughthe arbor of said pole spider.

3. A clock according to claim 1, characterized in that the poles of themagnet system are disposed, in a plane extending through the arbor ofthe pole spider and in that said pole spider is provided with an oddnumber of poles.

4. A clock according to claim 1 characterized in that the pole spider isprovided with radially projecting teeth the ends of which are bent offin the direction of rotation of said pole spider.

5. A clock according to claim 4, characterized in that the ends of theteeth of the pole spider are provided with lugs projecting at a rightangle in the direction of rotation.

6. A clock according to claim 1, characterized in that the oscillatorhas secured to it a horseshoe magnet which extends in a plane parallelto the pole spider and the poles of which are disposed oppositesubstantially diagonally opposed points of said pole spider.

7. A clock according to claim 1, characterized in that the oscillator isprovided with two horseshoe magnets, which each extend in a planeperpendicular to the pole spider and the poles of which envelope saidpole spider from two sides at one point each of two substantiallydiagonally opposed points of said pole spider.

8. A clock according to claim 7, characterized in that said magnets aredisposed at the ends of a U-shaped support.

9. A clock according to claim 6 characterized in that said magnet issecured to the end of a vibrating reed.

10. A clock according to claim 9, characterized in that said vibratingreed is formed by one leg of a tuning fork, the other leglof whichcarries an appropriate balance weight.

1. A clock according to claim 7, characterized in that the oscillator isformed by a tuning fork and in that the magnets are each secured to oneleg of said tuning fork.

12. A clock according to claim 1, characterized in that the v polespider is formed by a toothed disc of ferromagnetic material, inparticular sheet iron.

13. A clock according to claim 1, characterized in that the pole spiderconsists of a nonmagnetic material provided with ferromagnetic inserts,in particular radially or axially disposed pms.

1. An electric clock with a time-determining mechanical oscillatorexcited at its natural frequency and carrying a magnet system whichdrives the clock and the poles of which are disposed opposite twosubstantially diagonally opposed points of a nonmagnetized ferromagneticpole spider, said mechanical oscillator moving said poles insubstantially radial relation to said pole spider, to which a rotarymotion in synchronism with the movements of said oscillator is impArtedby the movements of said magnet system, characterized in that said polespider is provided with only one ring of poles along its circumference,and in that the poles of the magnet system are disposed so that theywill be located between two poles at one side of the pole spider whenthey are opposite one pole at the other side of that spider.
 2. A clockaccording to claim 1, characterized in that said pole spider is providedwith an even number of teeth, and in that said poles of said magnetsystem are displaced with respect to the plane extending through thearbor of said pole spider.
 3. A clock according to claim 1,characterized in that the poles of the magnet system are disposed, in aplane extending through the arbor of the pole spider and in that saidpole spider is provided with an odd number of poles.
 4. A clockaccording to claim 1 characterized in that the pole spider is providedwith radially projecting teeth the ends of which are bent off in thedirection of rotation of said pole spider.
 5. A clock according to claim4, characterized in that the ends of the teeth of the pole spider areprovided with lugs projecting at a right angle in the direction ofrotation.
 6. A clock according to claim 1, characterized in that theoscillator has secured to it a horseshoe magnet which extends in a planeparallel to the pole spider and the poles of which are disposed oppositesubstantially diagonally opposed points of said pole spider.
 7. A clockaccording to claim 1, characterized in that the oscillator is providedwith two horseshoe magnets, which each extend in a plane perpendicularto the pole spider and the poles of which envelope said pole spider fromtwo sides at one point each of two substantially diagonally opposedpoints of said pole spider.
 8. A clock according to claim 7,characterized in that said magnets are disposed at the ends of aU-shaped support.
 9. A clock according to claim 6 characterized in thatsaid magnet is secured to the end of a vibrating reed.
 10. A clockaccording to claim 9, characterized in that said vibrating reed isformed by one leg of a tuning fork, the other leg of which carries anappropriate balance weight.
 11. A clock according to claim 7,characterized in that the oscillator is formed by a tuning fork and inthat the magnets are each secured to one leg of said tuning fork.
 12. Aclock according to claim 1, characterized in that the pole spider isformed by a toothed disc of ferromagnetic material, in particular sheetiron.
 13. A clock according to claim 1, characterized in that the polespider consists of a nonmagnetic material provided with ferromagneticinserts, in particular radially or axially disposed pins.